This invention relates to means for reading an optical pattern containing one-dimensional or multi-dimensional characters.
Known optical reading equipment is used to read optical patterns by projecting a light onto the optical pattern. A light image reflected from the optical pattern is then projected onto an electronic scan type sensor, such as a photodetector, which converts the reflected light image into an electronic analog signal. The analog signal is then processed to read and recognize the optical pattern information.
A common optical pattern to be read is a barcode, comprised, typically, of a row of parallel stripes which may be, for example, black and white stripes of different shapes and with different spacing. However, use of optical reading apparatus is expanding in many fields, including, for example, various fields such as factory-automation, distribution channel, service system, etc. Furthermore, the volume of information to be recorded, read and processed is ever increasing. The increase in the information makes it difficult, if not impossible, to include the needed information in one row of a barcode. Therefore, it is now desirable to be able to read multi-row barcodes, 2-dimensional barcodes, letters, characters, and other high density codes.
Multi-dimensional information codes and symbols may be read by a scanner such as a TV camera system illustrated in FIG. 1. The TV camera system scanner in FIG. 1 includes a TV camera (21), an image processor (22) and a TV monitor (23). The image processor (22) is connected to a host computer (not shown) via a communication RS-232C line. In this kind of system an information label (24) is set to face the TV camera (21) and may be photographed by the TV camera (21) under normal room light illumination, and the photographed image is processed and converted by the image processor (22) and transmitted to the host computer. On the other hand, the data of the photographed image may also be displayed on a TV monitor (23) via a connecting cable.
Some problems associated with the prior art include the following: First, the TV camera (21), the image processor (22) and the TV monitor (23), etc. are expensive pieces of equipment. Second, a certain length of time is needed to prepare and focus the TV camera (21) to enable it to comply with the room illumination brightness. Third, a 2-dimensional area sensor, that converts the image of the TV camera (21) photoelectrically, has a limited effective number of pixels in the horizontal and vertical directions (e.g., 576 H.times.485 V). This limits the resolution capacity of the reading. In this respect the resolution capacity is meant for a minimum line width of a readable information pattern. Fourth, the reading apparatus, repeating the rotation of a mirror in such a function as stop-rotation-stop, is slower in its reading speed and its improvement is fundamentally difficult.
It is an object of the present invention to overcome problems associated with the prior art discussed above.
It is another object of the invention to use a line image sensor and to effectuate a high speed, two-dimensional, reading of an optical pattern by cyclically varying and moving the angle and/or the position of a movable reflecting mirror.
It is still another object of the invention to enable the accurate reading in a very short time of a "one-row" barcode as well as multi-row barcodes, 2-dimensional barcodes, letters and characters.
It is another object of the invention to enable the easy and accurate position setting and support of the reading apparatus and the aiming of the apparatus toward an object to be read.
It is another object of the invention to make use of a line image sensor having a large number of pixels arranged in a row to enable the reading of an optical pattern with greater resolution than can be done with conventional reading method by a TV camera.
Another object of the invention is to achieve fast reading of an optical pattern by the repeated back and forth movement and/or vibration of a movable reflecting mirror without a move-and-stop function.
Another object of the invention is to provide optical reading apparatus which is smaller in size, lighter in weight and less costly to manufacture than the prior art apparatus and which includes simplified and energy-saving means for providing swinging and/or vibratory motion.